Energy-Work-Power

In class this week, we talked about energy, work, and power. Energy is a scalar quantity, which means that it is only measure with magnitude, no direction. Energy is also conserved in an isolated system, which means that total E_in=E_out. Energy can be potential (energy of position), which can be expressed with the equation PE=(mass)(gravity)(height). Energy can also be kinetic (energy of motion), which is expressed with the equation KE=1/2(mass)(velocity) ². The unit of energy is Joules. Work is a change in energy, and can be written as W=(force)(distance). The units of work are Newton meters (Nm) or Joule (J). Power is the rate at which work is being done. Power can be written as P=∆Energy/∆Time. The units of Power are Joules/Second or Watts.

When I think of potential and kinetic energy, I think of something falling from a height. The picture below is of me jumping off my bed.

Knowing that my mass is 60kg, and gravity’s pull is 10m/s², and assuming my bed is 0.5m high, I can find my potential energy standing on my bed.

PE=mgh

PE=(60kg)(10m/s²)(0.5m)

PE=300 J

Using my mass, and assuming that when I fell I reached a velocity of 3.16m/s, I can find my kinetic energy right before I landed.

KE=1/2mv²

KE=1/2(60kg)(3.16m/s) ²

KE= 300 J